1. Field of the Invention
The present invention relates to a robot controller and a robot control method for moving each of standard moving parts of each of robots to each of synchronous operation positions respectively set and simultaneously performing operations of the robots.
2. Description of the Related Art
FIG. 23 is a drawing for explaining pressing equipment 6 of a related art. When two robots 1 and 2 are operated simultaneously and the operable ranges of the robots 1 and 2 are overlaid each other, it is necessary to prevent the robots 1 and 2 from mutual interference. As a related art, there is an art available for preventing interference using mutual communication of two robot controllers 3 and 4.
The pressing equipment 6 includes the first robot 1 for supplying a workpiece 8 before pressing to a pressing machine 7, the second robot 2 for collecting a pressed workpiece 9 from the pressing machine 7, the robot controllers 3 and 4 for respectively controlling the robots 1 and 2, and a programmable controller (abbreviated to PLC) 5 for giving an operation instruction to the robot controllers 3 and 4.
The first robot 1 holds the workpiece 8 from an unloading table 10 and arranges it at a pressing position p2 of the pressing machine 7. The second robot 2 collects the workpiece 9 arranged at the pressing position p2 of the pressing machine 7 and transfers it to the succeeding processing machine. Therefore, when the robots 1 and 2 are different in speed from each other, in the neighborhood of the pressing position p2 of the pressing machine 7 where the workpieces 8 and 9 are arranged, there is a fear of interference of the robots 1 and 2.
To prevent the robots 1 and 2 from interference, the first controller 3 stores information of a proximity position p1 on the upstream side of the pressing position p2 in the transfer direction. Further, the second controller 4 stores information of a separation position p3 on the downstream side of the pressing position p2 in the transfer direction. The first controller 3, on the basis of the information given from the second controller 4, judges whether the workpiece 8 can move into the neighboring space of the pressing machine 7 or not.
FIG. 24 includes graphs showing a change with time of the speed of each of the workpieces 8 and 9 of the robots 1 and 2. FIG. 24(1) shows a speed change of the robot hand of the first robot 1 and FIG. 24(2) shows a speed change of the robot hand of the second robot 2. As shown in FIG. 24(1), the first controller 3 stops the workpiece 8 before pressing at a point of time tp1 of arrival at the proximity position p1 where the workpiece 8 before pressing is moved. Further, as shown in FIG. 24(2), the second controller 24 moves the workpiece 9 after pressing at a point of time tp2 of arrival at the pressing position p2 where the workpiece 9 after pressing is held. And, the second controller 24 stops the workpiece 9 after pressing at a point of time tp3 of arrival at the separation position p3 where the workpiece 9 after pressing is moved.
And, at the point of time tp3 of arrival at the separation position, the second controller 4 transmits an arrival signal to the PLC 5. The PLC 5, upon receipt of the arrival signal from the second controller 4, gives a movement restart instruction to the controllers 3 and 4. The first controller 3, upon receipt of the arrival signal from the PLC 5, restarts the movement of the workpiece 8 before pressing from the proximity position p1 to the pressing position p2. Further, the second controller 4, upon receipt of the arrival signal from the PLC 5, restarts the movement of the workpiece 9 after pressing from the separation position p3 to the succeeding processing machine.
By such an operation, before the workpiece 9 after pressing is separated from the neighboring space of the pressing machine 7, the workpiece 8 before pressing is prevented from entrance into the neighboring space of the pressing machine 7. Therefore, the robots 1 and 2 can be prevented from interference with each other. This related art is disclosed, for example, in Japanese Patent Laid-Open Publication No. 7-271415.
In the related art aforementioned, the first robot 1 makes the workpiece 8 wait at the proximity position p1 at the proximity position arrival point of time tp1. And, after standby, when the workpiece 8 after pressing reaches the separation position arrival point of time tp3, the first robot 1 restarts the movement of the workpiece 8 before pressing. To prevent mutual interference of the robots 1 and 2, it is necessary to stop once them. The robots 1 and 2 are set to move as fast as possible to improve the production efficiency. In this case, even if the first robot 1 is moved at its maximum speed, if the workpiece 8 before pressing waits at the proximity position p1, compared with a case that the first robot 1 moves at a low speed and the workpiece 8 before pressing moves without stopping at the proximity position p1, the consumption of energy is increased and the energy efficiency is lowered.
Further, to prevent interference without keeping the workpiece 8 before pressing wait at the proximity position p1, it is considered to adjust manually the operation timing such as the robot speed so as to slow down the first robot 1. However, if the first robot 1 is excessively slowed down, even if the workpiece 9 after pressing reaches the separation position p3, a condition that the workpiece 8 before pressing does not reach yet the proximity position p1 is caused and a problem arises that the cycle time is increased.
Further, the timing adjustment by hand must be made whenever changing the equipment to be adjusted, workpiece shape held, movement posture, movement route, and movement position and cannot be decided uniformly. Therefore, a problem arises that the time required for preparation of the robot operation is increased. Further, also for the spot welding operation or painting operation by a plurality of robots, the similar problem is imposed.